The present invention relates to document authentication, and more particularly to the utilization of handwritten signatures in connection with electronically stored, transmitted, and retrieved data and documents.
Handwritten pen-on-paper signatures have been the basis of contracts in commerce for hundreds of years, for a variety of reasons, including:
1. The signature and documents are one in the same, being forever bound together by the ink being on the paper; PA1 2. The identity of the signer can be verified after the fact by a trained forensic document examiner who is skilled in the art and science of signature character analysis, and who can testify, be qualified, and be cross-examined in a court of law; and PA1 3. The signer can keep a copy or duplicate original of the contract to deter fraud. PA1 1. The signature envelopes cannot be verified by a forensic document examiner using traditional methods; PA1 2. The signature envelopes are not readily transportable to future systems, being based on arbitrary measurement statistics of the handwritten signatures; and PA1 3. The signature envelopes are ineffective to the extent that they omit information originally contained in the handwritten signature itself. PA1 (a) progressively capturing a handwritten signature as an ordered sequence of data corresponding to successive coordinates and corresponding timing of stylus movement producing the signature; PA1 (b) storing the data as an electronic signature; and PA1 (c) electronically binding the electronic signature to a stored counterpart of the document. PA1 (a) creating an encryption key by generating a cryptographic hash function of the stored counterpart of the document; and PA1 (b) encrypting the electronic signature to the encryption key. PA1 (a) capturing a handwritten signature as a sequence of data corresponding to coordinates of stylus movement producing the signature; PA1 (b) storing the data as an electronic signature; PA1 (c) creating an encryption key by generating a cryptographic hash function of a stored counterpart of the document; PA1 (d) encrypting the electronic signature to the encryption key, thereby electronically binding the electronic signature to a stored counterpart of the document; PA1 (e) identifying stored instances of the encryption key; and PA1 (f) erasing each stored instance of the encryption key. PA1 (a) encrypting the sequence of data to a fixed key of arbitrary length; and PA1 (b) storing the encrypted sequence as the electronic signature. PA1 (a) determining a date and time at which the handwritten signature was produced; and PA1 (b) including counterparts of the date and time with the electronic signature. PA1 (a) determining a set of document data associated with the document; PA1 (b) generating a cryptographic hash data string of arbitrary length from the document data; and PA1 (c) encrypting the electronic signature using the cryptographic hash data string. PA1 (a) creating a counterpart of the encryption key by generating another cryptographic hash function of the stored counterpart of the document; PA1 (b) decrypting the electronic signature using the encryption key, thereby electronically binding the electronic signature to a stored counterpart of the document; PA1 (c) identifying stored instances of the encryption key; and PA1 (d) erasing each stored instance of the encryption key. PA1 (a) capturing a handwritten signature as a sequence of data corresponding to coordinates of stylus movement producing the signature; PA1 (b) storing the data as an electronic signature; PA1 (c) creating a signature receipt as a cryptographic hash function of the electronic signature; PA1 (d) creating a document receipt as a cryptographic hash function of a stored counterpart of the document; and PA1 (e) producing counterparts of the signature and document receipts. PA1 (e) embedding the signature receipt into the document; and PA1 (f) embedding the document receipt into the electronic signature, thereby to form a cross-linked binding of the signature with the document. PA1 (a) providing a transportable file medium; PA1 (b) copying counterparts of the document receipt and the signature receipt on the file medium; and PA1 (c) delivering the file medium having the receipt counterparts to a signer of the document. PA1 (a) capturing a second electronic signature as a stored sequence of data corresponding to coordinates of stylus movement producing second handwritten signature; PA1 (b) simultaneously displaying in locational proximity graphic counterparts of the first and second electronic signatures; PA1 (c) displaying, for each of the graphic counterparts, a cursor being positioned along a line segment of the signature and oriented perpendicular to the line segment; and PA1 (d) for each of the graphic counterparts, moving the cursor relative to the signature in response to operator input. PA1 (a) determining at least one measurement parameter relative to the line segment at which the cursor is located; and PA1 (b) displaying a digital representation of the parameter.
In the continuing development of electronic document storage and retrieval, a recognized need is inclusion of legally effective signatures for creating legally binding electronic records. Early systems addressing this need utilized a simple image of a signature (such as a bit map) being affixed to a document as a picture of a signature. This approach had the disadvantage that the bit map image of the signature is difficult to verify as being directly from the hand of the signer, in that little if any dynamic data is present. Also, an image of a signature can easily be scanned from an existing document or record and improperly inserted into a document as a forgery.
Later systems included computer algorithms for verifying a signature prior to the user being able to sign an electronic document. Problems with this method include the need to enrol the signer into an electronic verification unit of the system prior to use, the potential for errors in the verification algorithm, and the inability to demonstrate the accuracy of verification of a signature to a layperson or in a court of law. Further, the signatures are typically not transportable to systems having different algorithms without loss of data precision.
U.S. Pat. No. 5,544,255 to Smithies et al. Discloses a computer-based system for capturing and verifying a handwritten signature of an electronically stored document by capturing the signature and storing a set of statistical measurements in a signature envelope that can contain a checksum of the document. The measurements can include shape, number of pen strokes, total line length, average stroke length, number of acceleration and deceleration maxima events, the overall time taken to complete the signature, and the pen down time. The system can also contain a database of known signature measurement templates to be compared with a submitted signature to produce a similarity score. The system if Smithies at al. is not entirely satisfactory; for example:
Thus there is a need for an electronic document signature system that is effective, reliable, easily verifiable, resistant to forgery, and easy to use, and that otherwise overcomes the disadvantages of the prior art.